Open-column liquid chromatography

In open-column liquid chromatography, the test sample is added to the top of a column packed with adsorbent material (e.g. alumina, silica gel, polymer gel or fine-particle substrate coated with an organic compound). Differential movement 

HPLC units have been interfaced with a wide range of detection techniques (e.g. spectrophotometry, fluorimetry, refractive index measurement, voltammetry and conductance) but most of them only provide elution rate information. As with other forms of chromatography, for component identification, the retention parameters have to be compared with the behaviour of known chemical species. For organo-metallic species element-specific detectors (such as spectrometers which measure atomic absorption, atomic emission and atomic fluorescence) have proved quite useful. The state-of-the-art HPLC detection system is an inductively coupled plasma/MS unit. HPLC applications (in speciation studies) include determination of metal alkyls and aryls in oils, separation of soluble species of higher molecular weight, and separation of As111, Asv, mono-, di- and trimethyl arsonic acids. There are also procedures for separating mixtures of oxyanions of N, S or P. 

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Principles and Characteristics Column liquid chromatography is the parent of all other types of chromatography. The technique used by Tswett is now called classical open-column liquid chromatography or simply LC. In column chromatography the stationary phase is contained in a column and the mobile phase flows... 

Traditional open column liquid chromatography (LC) suffers poorly in comparison with the thin layer method in that it is a fairly slow process which requires large amounts of packing material, eluant and sample. The major disadvantages of LC methods are with speed, scale, resolution and characterisation. 

The hydrocarbon ("oil") fraction of a coal pyrolysis tar prepared by open column liquid chromatography (LC) was separated into 16 subfractions by a second LC procedure. Low voltage mass spectrometry (MS), infrared spectroscopy (IR), and proton (PMR) as well as carbon-13 nuclear magnetic resonance spectrometry (CMR) were performed on the first 13 subfractions. Computerized multivariate analysis procedures such as factor analysis followed by canonical correlation techniques were used to extract the overlapping information from the analytical data. Subsequent evaluation of the integrated analytical data revealed chemical information which could not have been obtained readily from the individual spectroscopic techniques. The approach described is generally applicable to multisource analytical data on pyrolysis oils and other complex mixtures. 

Our method for the quantitative analysis of lAA consists of four major steps 1) extraction, 2) prepurification, 3) HPLC, and 4) GC-MS. The major time-consuming steps are the purification steps prior to GC-MS. The traditional prepurification [1, 11] has involved solvent partitioning steps and, in some protocols, open column liquid chromatography. Use of high resolution bonded phase capillary GC columns has allowed increased sensitivity at the mass spectral step, and the use of 3 and 5 /xm HPLC packings has made it reasonable to use shorter columns, thus reducing the time required for HPLC. The improvement in recovery afforded by the shorter HPLC columns and the improved sensitivity of capillary GC-MS suggested to us that it was possible to scale down the sample size to a level that made practical the use of Sep-Pak-Mko disposable mini-columns for sample preparation [2, 6, 7]. 

Svensson, L. M. and Markides, K. E., Fiber optic-based UV-absorption detector cell for high-temperature open tubular column liquid chromatography,... 

Fujimoto, C., Sakurai, M., and Muranaka, Y. (1999). PEEK columns for open-tubular liquid chromatography with electroosmotic flow. /. Microcolumn Sep. 11, 693-700. 

Figure 15. Open tubular liquid chromatography of amine-NBD derivatives using on-column fluorescence detection. Peaks correspond from left to right to ethylamine, n-propylamine, n-butylamine, cyclohexylamine, and n-hexylamine. Conditions 20-p.m X 8.3-m column with C-18 bonded phase 20% acetonitrile and 80% water (v/v) mobile phase at a linear velocity of 0.50 cm/s on-column injection of 5 nL. (Reproduced from reference 59. Copyright 1984 American Chemical Society.)...

The liquid products were analysed by capillary gas chromatography (GC) and peak identifications were made with the aid of GC-MS used in conjunction with concentration of the aromatic species by open-column adsorption chromatography on alumina. To give a clear indication of the boiling point distribution of the products, the peaks in the chromatograms have been grouped using successive n-alkanes. This procedure could not be used as precisely for the n-hexadecane/quinoline mixtures because of overlap of the quinoline and product peaks close to Cu,... 

The same group developed an open-tubular liquid chromatography (OTLC) column by chemically binding BSA to the inner surface of a fused-silica capillary [222]. A number of enantioseparations have been presented, including DNP-amino acids and 3-hydroxy-1,4-benzodiazepines. 

The process of band broadening (Figure 2.1) is measured by the column efficiency or the number of theoretical plates N, equation (2.24)), which is equal to the square of the ratio of the retention time to the standard deviation of the peak. In theory, the value of N for packed columns has only a small dependency on k and may be considered to be a constant for a particular column. Column efficiency in open-tubular systems decreases markedly with increased retention. For this reason open-tubular liquid chromatography systems must be operated at relatively low kf values (see section 2.5.S.2). 

Column-liquid chromatography (CLC) can be conveniently divided into those systems which use packed columns and those which use open tubes (Figure 3.1). Capillary tubes (<4 < 350 pm) are used in open-tubular chromatography and the stationary phase is coated on the internal surface. Packed-column systems can be sub-divided arbitrarily into capillary columns, microbore columns, analytical columns and preparative columns according to the internal diameter of the column (Figure 3.1). 

Knecht, L.A. Guthrie, E.J. Jorgenson, J.W. On-column electrochemical detector with a single graphite fiber electrode for open-tubular liquid chromatography. Anal. Chem. 1984, 56, 479 82. 

The Golay equation can also be used to predict optimum separation conditions in open tubular column liquid chromatography [128,129]. The main difference between... 

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